CExprEntityField::checkAggregation

static function checkAggregation($expr)
{
	if (empty(self::$aggrFunctions))
	{
		self::$aggrFunctions = array_unique(array_merge(
			self::$aggrFunctionsMYSQL, self::$aggrFunctionsMSSQL, self::$aggrFunctionsORACLE
		));
	}

	preg_match_all('/(?:^|[^a-z0-9_])('.join('|', self::$aggrFunctions).')[s(]+/i', $expr, $matches);

	return $matches[1];
}